Methods, apparatuses, and computer program products for out-of-band sensing in a cognitive lte system

ABSTRACT

Provided are methods, corresponding apparatuses, and computer program products for performing out-of-band sensing on an unlicensed frequency band. A method comprises sending a configuration message for configuring measurement on at least one channel in a frequency band of a primary system; receiving a measurement report made based upon the configuration message; and determining the usability of the at least one channel based upon the measurement report, wherein the configuration message includes information regarding a respective predetermined threshold of energy detection or primary-system-feature detection, and the measurement report is for reception when a measured energy detection value or a measured primary-system-feature detection value of a received signal on the at least one channel is less than the respective predetermined threshold. With the claimed inventions, the spectrum efficiency would be improved and interference between a secondary system and an LTE system could be alleviated.

FIELD OF THE INVENTION

Embodiments of the present invention generally relate to wirelesscommunication techniques including the 3GPP (the 3rd GenerationPartnership Project) LTE (Long Term Evolution) technique. Moreparticularly, embodiments of the present invention relate to methods,apparatuses, and computer program products for out-of-band sensing in acognitive LTE system.

BACKGROUND OF THE INVENTION

Various abbreviations that appear in the specification and/or in thedrawing figures are defined as below:

ATSC Advanced Television System Committee

BS Base Station

BPSK Binary Phase Shift Keying

CA Carrier Aggregation

CP Cyclic Prefix

CR Cognitive Radio

CDMA Code Division Multiple Access

DTV Digital Television

DFT Discrete Fourier Transform

eNB evolved Node B

FFT Fast Fourier Transform

ISDB Integrated Services Digital Broadcasting

OFDM Orthogonal Frequency Division Multiplexing

PSD Power Spectral Density

QP Quiet Period

QPSK Quadrature Phase Shift Keying

RSRP Reference Signal Receiving Power

RSRQ Reference Signal Receiving Quality

SQPSK Staggered Quadrature Phase-Shift Keying

TVWS TV White Spaces

UE User Equipment

VSB Vestigial Side Band

WLAN Wireless Local Network

WiFi Wireless Fidelity

WiMax Worldwide Interoperability for Microwave Access

An LTE system has been accepted as a world-wide standard for wirelesscommunications and it has capabilities of a peak download data rate of 1Gbps, wide transmission bandwidth, low C-plane latency, increased userthroughput and spectrum flexibility or the like. However, the LTE systemalso suffers from a bandwidth scarcity problem which has been verycommon in wireless communications. To alleviate this problem and boostspectrum efficiency, a CR technique has evoked considerable researchinterests lately because it is capable of efficiently utilizing unused“spectrum holes” on unlicensed bands without causing severe interferenceto primary users. Meanwhile, a CA technique is being standardized in the3GPP as part of the LTE Release 10, which allows for aggregatingnon-contiguous spectrum fragments across multiple carriers. Therefore,incorporating CR features into the LTE system with the CA technique hasbecome an efficient solution for solving the above spectrum scarcityproblem.

Many researches with respect to the CR technique have been focusing onthe TVWS. The database approach for TVWS access is considered as a toolto find available spectrum bands, which requires less investment otherthan an incumbent database that maintains data about used frequencies inthe TV band. As compared to the database approach, spectrum sensing hasits own advantages in respect of detecting more access opportunities forsecondary systems working under a primary system. Besides, the databaseapproach is always based upon coarse-grained allocation techniques andthus inferior to the spectrum sensing in determining whether a givenchannel is actually available. Furthermore, the spectrum sensing couldbe used to update and improve the database as appropriate.

In the CR-enabled networks, reliably obtaining available spectrum holesby the spectrum sensing (working independently or assisting thedatabase) is crucial for secondary systems to access unlicensed bandsopportunistically. As specified in IEEE 802.22 standard “IEEEP802.22™/D0.1, “Draft Standard for Wireless Regional Area Networks Part22: Cognitive Wireless RAN Medium Access Control (MAC) and PhysicalLayer (PHY) specifications: Policies and procedures for operation in theTV Bands,” which is incorporated herein by reference in its entirety,out-of-band spectrum sensing refers to the case when an incumbentsensing activity is carried out in those channels other than workingchannels, aiming at obtaining available spectrum resource. This does notneed a network level QP, and is a similar procedure to aninter-frequency measurement in LTE systems.

As specified in TS 36.3313GPP V10.3.0 (2011-09) Evolved UniversalTerrestrial Radio Access (E-UTRA); Radio Resource Control (RRC) (Release10), which is also incorporated herein by reference in its entirety, aUE can be requested to perform intra-frequency, inter-frequency orinter-RAT measurements, and the measurement configuration includes thefollowing parameters: measurement objects, reporting configurations,measurement identities, quantity configurations, and measurement gaps.According to different measurement purposes, the criteria for triggeringthe UE to send a measurement report are different. For instance, if thetrigger type is set to event, Events A1/2 are for serving cellmeasurements, Events A3/4/5/6 are for intra/inter-frequency measurementsand CA, as well as Event B1/2 are for inter-RAT measurements. However,in a cognitive LTE network, the conventional inter-frequencymeasurements cannot enable out-of-band spectrum sensing. This is becausethe measurement quantity of conventional inter-frequency measurement isRSRP/RSRQ in neighbor cells, and the decision condition is alwaysdependent on whether the quality of a neighbor cell is better than apredetermined threshold. However, for the out-of-band spectrum sensing,the sensing target is the energy or feature of a received signal on anunlicensed band, where there may not be any reference signals like thosetransmitted in the LTE system. Therefore, the out-of-band spectrumsensing cannot be exploited simply by reusing the current measurementconfiguration in the LTE system, and new measurement configurationsshould be developed for cognitive radio based LTE systems

In view of the above, it would be desirable to configure out-of-bandsensing in a cognitive LTE network without significant changes to theexisting LTE architecture and spectrum efficiency could be improved bysuch out-of-band sensing. Further, the out-of-band sensing would notbring about interference to the primary or secondary system.

SUMMARY OF THE INVENTION

Therefore, there is a need in the art to provide for an efficient way ofperforming out-of-band sensing in a cognitive LTE network such thatcommunication channels licensed to a primary system could be used by theLTE network without interference therebetween.

In an exemplary embodiment of the present invention, a method isprovided, which comprises sending a configuration message forconfiguring measurement on at least one channel in a frequency band of aprimary system. The method also comprises receiving a measurement reportmade based upon the configuration message. In addition, the methodcomprises determining the usability of the at least one channel basedupon the measurement report, wherein the configuration message includesinformation regarding a respective predetermined threshold of energydetection or primary-system-feature detection, and the measurementreport is for reception when a measured energy detection value or ameasured primary-system-feature detection value of a received signal onthe at least one channel is less than the respective predeterminedthreshold.

In one embodiment, the configuration message includes the informationregarding the respective predetermined threshold of the energy detectionand the method comprises receiving the measurement report sent when themeasured energy detection value is less than the respectivepredetermined threshold and determining that the at least one channel isusable for cellular communication based upon the measurement report.

In another embodiment, the configuration message includes informationregarding the respective predetermined threshold of the energy detectionand the method comprises receiving the measurement report sent when themeasured energy detection value is less than the respectivepredetermined threshold; sending a further configuration messageincluding information regarding the respective predetermined thresholdof the primary-system-feature detection; receiving a further measurementreport sent when a measured primary-system-feature detection value isless than the respective predetermined threshold; and determining theprimary system is absent based upon the further measurement report.

In an additional embodiment, the configuration message includesinformation regarding the respective predetermined threshold of theenergy detection and the method comprises receiving the measurementreport sent when a measured energy detection value is less than therespective predetermined threshold; sending a further configurationmessage for periodical reception of a measurement report regarding ameasured primary-system-feature detection value; periodically receivingthe measurement report regarding the measured primary-system-featuredetection value; and determining whether the primary system is presentbased upon the periodically received measurement report.

In a further embodiment, signal strength of the primary system is lowerthan noise strength of a UE.

In one embodiment, the configuration message includes informationregarding the respective predetermined threshold of theprimary-system-feature detection and the method comprises receiving themeasurement report sent when the primary-system-feature detection valueis less than the respective predetermined threshold; determining, basedupon the measurement report, that the at least one channel has alikelihood of being used by a potential secondary system; sending afurther configuration message for periodical reception of a measurementreport regarding a measured secondary-system-feature detection value;periodically receiving the measurement report regarding the measuredsecondary-system-feature detection value; and determining whether toshare the at least one channel with the potential secondary system basedupon the periodically received measurement report.

In an additional embodiment, the configuration message includesinformation regarding the respective predetermined threshold of theenergy detection and the method comprises sending, if no reception of ameasurement report sent when the energy detection value is less than therespective predetermined threshold, a further configuration messageincluding information regarding the respective predetermined thresholdof the primary-system-feature detection; receiving a measurement reportsent when the primary-system-feature detection value is less than therespective predetermined threshold; and determining the primary systemis absent based upon the received measurement report.

In yet another embodiment, the configuration message includesinformation regarding the respective predetermined threshold of theenergy detection and the method comprises sending, if no reception of ameasurement report sent when the energy detection value is less than therespective predetermined threshold, a further configuration message forperiodical reception of a measurement report regarding a measuredprimary-system-feature detection value; periodically receiving themeasurement report regarding the measured primary-system-featuredetection value; and determining whether the primary system is presentbased upon the periodically received measurement report.

In a further embodiment, no measurement report is for reception and themethod further comprises sending a further configuration message forperiodical reception of a measurement report regarding a measuredprimary-system-feature detection value or a measuredsecondary-system-feature detection value; periodically receiving themeasurement report regarding the measured primary-system-featuredetection value or the measured secondary-system-feature detectionvalue; determining whether the primary system or the secondary system ispresent based upon the periodically received measurement report; anddetermining, if the primary system is absent and the secondary system ispresent, whether to share the at least one channel with the secondarysystem.

In one embodiment, the measurement report includes informationindicative of the at least one channel.

In another exemplary embodiment of the present invention, a method isprovided, which comprises measuring an energy detection value or aprimary-system-feature detection value of a received signal on at leastone channel in a frequency band of a primary system. The method alsocomprises sending a measurement report when the measured energydetection value or primary-system-feature detection value of thereceived signal on the at least one channel is less than a respectivepredetermined threshold of energy detection or primary-system-featuredetection.

In another embodiment, the measuring is based upon a configurationmessage received from a BS and the configuration message includes therespective predetermined threshold of the energy detection orprimary-system-feature detection.

In an additional embodiment, the sending the measurement reportcomprises sending the measurement report when the measured energydetection value is less than the respective predetermined threshold andthe method further comprises measuring the primary-system-featuredetection value of the received signal on the at least one channel; andsending a measurement report when the primary-system-feature detectionvalue is less than the respective predetermined threshold.

In a further embodiment, the sending the measurement report comprisessending the measurement report when the measured energy detection valueis less than the respective predetermined threshold and the methodfurther comprises measuring the primary-system-feature detection valueof the received signal on the at least one channel; and periodicallysending a measurement report regarding the primary-system-featuredetection value.

In yet another embodiment, signal strength of the primary system islower than noise strength of a UE.

In a further embodiment, the measured energy detection value andprimary-system-feature detection value are not less than the respectivepredetermined thresholds and the method further comprises measuring theprimary-system-feature detection value of the received signal on the atleast one channel; and periodically sending a measurement reportregarding the primary-system-feature detection value.

In one embodiment, the primary-system-feature detection value is lessthan the respective predetermined threshold and the method furthercomprises: measuring a secondary-system-feature detection value of thereceived signal on the at least one channel; and periodically sending ameasurement report regarding the secondary-system-feature detectionvalue.

In another embodiment, the periodically sending is based upon a furtherconfiguration message received from a BS and the further configurationmessage is for configuring periodical sending of a measurement report.

In a further embodiment, the measurement report includes informationindicative of the at least one channel.

In an additional exemplary embodiment of the present invention, anapparatus is provided, which comprises means for sending a configurationmessage for configuring measurement on at least one channel in afrequency band of a primary system. The apparatus also comprises meansfor receiving a measurement report made based upon the configurationmessage. In addition, the apparatus comprises means for determining theusability of the at least one channel based upon the measurement report,wherein the configuration message includes information regarding arespective predetermined threshold of energy detection orprimary-system-feature detection, and the measurement report is forreception when a measured energy detection value or a measuredprimary-system-feature detection value of a received signal on the atleast one channel is less than the respective predetermined threshold

In a further exemplary embodiment of the present invention, an apparatusis provided, which comprises means for measuring an energy detectionvalue or a primary-system-feature detection value of a received signalon at least one channel in a frequency band of a primary system. Theapparatus also comprises means for sending a measurement report when themeasured energy detection value or primary-system-feature detectionvalue of the received signal on the at least one channel is less than arespective predetermined threshold of energy detection orprimary-system-feature detection.

In one exemplary embodiment of the present invention, an apparatus isprovided, which comprises at least one processor and at least one memoryincluding computer program code. The memory and the computer programcode are configured to cause the apparatus to send a configurationmessage for configuring measurement on at least one channel in afrequency band of a primary system. The memory and the computer programcode are also configured to cause the apparatus to receive a measurementreport made based upon the configuration message. In addition, thememory and the computer program code are configured to cause theapparatus to determine the usability of the at least one channel basedupon the measurement report, wherein the configuration message includesinformation regarding a respective predetermined threshold of energydetection or primary-system-feature detection, and the measurementreport is for reception when a measured energy detection value or ameasured primary-system-feature detection value of a received signal onthe at least one channel is less than the respective predeterminedthreshold.

In another exemplary embodiment of the present invention, an apparatusis provided, which comprises at least one processor and at least onememory including computer program code. The memory and the computerprogram code are configured to cause the apparatus to measure an energydetection value or a primary-system-feature detection value of areceived signal on at least one channel in a frequency band of a primarysystem. The memory and the computer program code are also configured tocause the apparatus to send a measurement report when the measuredenergy detection value or primary-system-feature detection value of thereceived signal on the at least one channel is less than a respectivepredetermined threshold of energy detection or primary-system-featuredetection.

In another exemplary embodiment of the present invention, a computerprogram product is provided, which, comprises at least one computerreadable storage medium having a computer readable program code portionstored thereon. The computer readable program code portion comprisesprogram code instructions for sending a configuration message forconfiguring measurement on at least one channel in a frequency band of aprimary system. The computer readable program code portion alsocomprises program code instructions for receiving a measurement reportmade based upon the configuration message. In addition, the computerreadable program code portion comprises program code instructions fordetermining the usability of the at least one channel based upon themeasurement report, wherein the configuration message includesinformation regarding a respective predetermined threshold of energydetection or primary-system-feature detection, and the measurementreport is for reception when a measured energy detection value or ameasured primary-system-feature detection value of a received signal onthe at least one channel is less than the respective predeterminedthreshold.

In one exemplary embodiment of the present invention, a computer programproduct is provided, which, comprises at least one computer readablestorage medium having a computer readable program code portion storedthereon. The computer readable program code portion comprises programcode instructions for measuring an energy detection value or aprimary-system-feature detection value of a received signal on at leastone channel in a frequency band of a primary system. The computerreadable program code portion also comprises program code instructionsfor sending a measurement report when the measured energy detectionvalue or primary-system-feature detection value of the received signalon the at least one channel is less than a respective predeterminedthreshold of energy detection or primary-system-feature detection.

According to certain embodiments of the present invention, by means ofsetting a new measurement configuration for cognitive radio based LTEsystems, the LTE system could detect other interferences on unlicensedbands where other systems (e.g., secondary systems) may operate and thusthe proposed new measurements enable better use of unlicensed or TVWSbands. For instance, the LTE system is capable of relatively accuratelyascertaining the status of the networks and may opportunistically accessunlicensed bands through the new measurement configuration. Further, itis easy to specify the proposed measurement mechanism withoutsignificantly affecting the existing LTE measurement approaches. Inaddition, flexibility and efficiency for use of the spectrum resourceswould be ameliorated.

Other features and advantages of the embodiments of the presentinvention will also be understood from the following description ofspecific embodiments when read in conjunction with the accompanyingdrawings, which illustrate, by way of example, the principles ofembodiments of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments of the invention that are presented in the sense ofexamples and their advantages are explained in greater detail below withreference to the accompanying drawings, in which:

FIG. 1 is a flow chart schematically illustrating a method forperforming out-of-band sensing on an unlicensed frequency band from a BSperspective according to an embodiment of the present invention;

FIG. 2 is a flow chart schematically illustrating a method forperforming out-of-band sensing on an unlicensed frequency band from a UEperspective according to another embodiment of the present invention;

FIG. 3 schematically illustrates signaling process of out-of-bandsensing in a cognitive LET system according to an embodiment of thepresent invention;

FIG. 4 is a schematic diagram illustrating some events that may arise ina cognitive LTE system;

FIG. 5 is a flow chart schematically illustrating in detail a method forperforming out-of-band sensing on an unlicensed frequency band accordingto another embodiment of the present invention; and

FIG. 6 is a schematic block diagram of a BS and a UE that are suitablefor use in practicing the exemplary embodiments of the presentinvention.

DETAILED DESCRIPTION OF EMBODIMENTS

While the making and using of various embodiments of the presentinvention are discussed in detail below, it should be appreciated thatthe present invention provides many applicable inventive concepts thatcan be embodied in a wide variety of specific contexts. The specificembodiments discussed herein are merely illustrative of specific ways tomake and use the invention and do not delimit the scope of theinvention.

To facilitate the understanding of this invention, a number of terms aredefined below. Terms defined herein have meanings as commonly understoodby a person of ordinary skill in the areas relevant to the presentinvention. Terms such as “a,” “an” and “the” are not intended to referto only a singular entity, but include the general class of which aspecific example may be used for illustration. The terminology herein isused to describe specific embodiments of the invention, but their usagedoes not delimit the invention. For example, a BS in the presentinvention may refer to one of a NB, an eNB, a base transceiver station,a radio BS, and the like and thus they may be used interchangeablythroughout the specification and claims as appropriate.

Embodiments of the present invention propose an efficient mechanism ofout-of-band sensing in a cognitive LTE system, which generally involvessensing configuring, out-of-band sensing, and sensing results reportingprocedures. In particular, various embodiments of the present inventionenable, through energy or feature detection, a cognitive measurementprocedure for the out-of-band sensing on unlicensed bands in cognitiveLTE systems. At the outset, a BS (e.g., an eNB) may obtain a list ofpossible idle channels on unlicensed bands such as a C-band or a TVWSband, and information about their usage. This could be implemented bye.g., accessing a database such as one in the TVWS or based uponhistorical or experimental data. Then, the eNB may configure, via one ormore configuration messages (i.e., signaling messages), one or more UEsto carry out cognitive measurement procedures for the out-of-handsensing of the channels on the unlicensed bands.

Based upon the results of the cognitive measurement procedures, the eNBmay determine whether the measured channels are useable for cellularcommunications. The cognitive measurement procedure for the out-of-bandsensing has two main phases: first, the eNB configures the UE toselectively perform two kinds of event-triggered measurement procedures,as referred to as C1 and C2 events for simplicity, to detect whether thechannel is idle or may have been occupied by a potential secondarysystem; second, if the sensed channel has been occupied by the secondarysystem, the eNB may further distinguish the secondary system byconfiguring the UE to carry out a further periodical measurement reportprocedure. Afterwards, the eNB may collect or receive measurementreports from UEs and make a final decision on the status and usabilityof the sensed channel. Optionally, the eNB may report the final decisionto the database for update.

Embodiments of the present invention will be described in detail asbelow.

FIG. 1 is a flow chart schematically illustrating a method 100 forperforming out-of-band sensing on an unlicensed frequency band from a BSperspective according to an embodiment of the present invention. Asillustrated in FIG. 1, the method 100 begins at step S101 and proceedsto step S102 at which the method 100 sends a configuration message forconfiguring measurement on at least one channel in a frequency band of aprimary system. The configuration message includes information regardinga respective predetermined threshold of energy detection orprimary-system-feature detection, and the measurement report is forreception when a measured energy detection value or a measuredprimary-system-feature detection value of a received signal on the atleast one channel is less than the respective predetermined threshold.

In particular, the BS may configure, via the configuration message,different parameters regarding the out-of-band sensing to the UE, whichmay include but are not limited to: a) unlicensed bands or channels tobe sensed in a frequency band (e.g. a TV band, a radar band, and asatellite C-band) as licensed to primary systems; b) quantities to bemeasured (e.g. energy or feature detection values of a received signalon the band or channel to be sensed); c) reporting criterions or types,e.g., event-triggered (e.g., C1 or C2 event as discussed later) orperiodical reporting. Then, it is quite straightforward to set anappropriate time to trigger, a measurement gap, and etc. In someimplementations, information about the signal features of a targetprimary system or a potential secondary system, which may be workingunder the target primary system, and information about a possibleavailable channel list on unlicensed bands may be retrieved from adatabase (such as used by the TVWS), if any.

As noted previously, to enable an efficient reporting mechanism, twoevent-triggered reporting procedures are proposed, in which oneprocedure is triggered on the condition that the energy detection valueof the received signal on the channel is less than a predeterminedthreshold and the other one is triggered on the condition that thefeature detection value of the received signal at issue is less than apredetermined threshold. For simplicity, these two conditions arereferred to hereinafter as events “C1” and “C2,” as will be discussed indetail as below.

Event C1

Energy Detection Value being Lower than a Predetermined Threshold

When a UE, which has a capability referred to as cognitive radiocapability, has been configured by an eNB to report a measurement reportfor the out-of-band sensing upon a trigger of the event C1, the UE wouldsend a measurement report regarding the energy detection value when thefollowing inequality C1-1 is fulfilled:

Med+Hys<Ted,  (C1-1)

where an item Med denotes a measurement result of the sensed or measuredchannel by energy detection; an item Hys denotes a hysteresis parameterfor the C1 event; and an item Ted denotes a threshold parameter of asensing algorithm for the event C1.

Based upon the measurement report, the BS would determine that thesensed channel may be idle and thus suitable for cellularcommunications, e.g., for CA or opportunistic secondary access. Unlikethe existing neighboring cell RSRP/RSRQ measurement whose resultingmeasurement report is triggered if the measured value is greater than apredetermined threshold, embodiments of the present invention proposetriggering the reporting if the measured value is less than apredetermined threshold so as to efficiently determine the presence ofthe primary system.

Alternatively or additionally, if the inequality C1-1 is regarded as anentering condition for the event C1, i.e., the sensed channel isaccepted as an usable unlicensed channel by the BS, then a leavingcondition for the event C1 may be defined as the below inequality C1-2:

Med−Hys>Ted,  (C1-2)

In some implementations, once the energy detection value, which had metthe inequality C-1, is now meeting the inequality C1-2, the UE may alsosend to the BS a measurement report. Based upon the received measurementreport, the BS would be aware that the energy detection value of thechannel has become larger than before and this may imply that theprimary system may be present and thus the sensed channel cannot be usedany longer by other systems lest incurring interference. In other words,it is time for this sensed channel to “leave” (i.e., be removed) from apreviously recorded list of usable unlicensed channels.

In practice, the threshold Ted is set not to be the target sensitivityfor the UEs to detect signals of the primary system but a little looseror higher than the sensitivity. This is because the primary systemdetection sensitivity may be much lower than the local noise in UEs. Forexample, the target sensitivity as specified in IEEE 802.22 for thedevices to detect TV signals is directed to signal strength of −116 dBm,and the level of the local noise in UEs of the LTE systems is −90 dBm.This is to say, when the primary TV transmitter is far away from acertain UE, its signal may be submerged under the local noise of the UE.However, the TV receiver may be close to the UE. If this is the case,the UE cannot detect the existence of the primary TV system and itstransmission will cause severe interference to the adjacent primary TVuser. In view of this, it would be preferable to set a looser energythreshold first and then utilize a feature detection (i.e., on a C2event basis) as a supplement to get rid of false alarms, and alsodistinguish a primary system and other secondary systems.

Event C2

Signal Feature Detection Value being Lower than a PredeterminedThreshold

Inequalities C2-1 and C2-2 as below are also introduced into the eventC2-1 to assist the UE in determining whether or not to send ameasurement report to the BS.

Mfd+Hys<Tfd,  (C2-1)

where an item Mfd denotes an measurement result of the feature detectionof the sensed channel; an item Hys denotes a hysteresis parameter forthe event C2; and an item Tfd denotes a threshold parameter of a sensingalgorithm for the event C2.

Once the inequality C2-1 is met, i.e., the measured feature detectionvalue Mfd is less than the predetermined threshold Tfd, the UB may senda measurement report to the BS. Based upon the measurement report, theBS may determine that the primary system may be absent and potentialsecondary systems may exist. Thus, the BS may conduct further actions,such as configuring the UE to perform measurements of feature detectionvalues of the secondary system and to periodically report themeasurement results regardless of the event C2. Similar to the event C1,if the inequality C2-1 is regarded as an entering condition and then thebelow inequality C2-2 may be regarded as a leaving condition:

Mfd−Hys>Tfd,  (C2-2)

Returning to FIG. 1, subsequent to completing step S102, the method 100proceeds to step S103, at which the method 100 receives a measurementreport made based upon the configuration message. Upon receipt of themeasurement report, the method 100 proceeds to step S104, at which themethod 100 determines the usability of the at least one channel basedupon the measurement. Finally, the method 100 ends at step S105.

In some embodiments, the configuration message includes the informationregarding the respective predetermined threshold of the energy detection(e.g., the item Ted in the inequality C1-1) and the method 100 receivesthe measurement report sent when the measured energy detection value isless than the respective predetermined threshold and determines that theat least one channel is usable for cellular communication based upon themeasurement report. In other words, the BS receives the measurementreport sent on an event C1 basis.

In some embodiments, for those primary systems whose signal strength islower than noise strength of the UE, e.g., a TV system, theconfiguration message includes information regarding the respectivepredetermined threshold of the energy detection and the method 100receives the measurement report sent when the measured energy detectionvalue is less than the respective predetermined threshold (i.e.,triggered by a C1 event). Then, the method 100 sends a furtherconfiguration message including information regarding the respectivepredetermined threshold of the primary-system-feature detection (e.g.,the item Tfd in the inequality C2-1). Upon receipt of a furthermeasurement report sent when a measured primary-system-feature detectionvalue is less than the respective predetermined threshold (i.e.,triggered by a C2 event), the method 100 determines the primary systemis absent based upon the further measurement report.

Alternatively, upon receipt of the measurement report sent when ameasured energy detection is less than the respective predeterminedthreshold, the method 100 sends a further configuration message forperiodical reception of a measurement report regarding a measuredprimary-system-feature detection value. Afterwards, upon periodicalreceipt of the measurement report regarding the measuredprimary-system-feature detection value, the method 100 determineswhether the primary system is present based upon the periodicallyreceived measurement report.

By means of the two manners as discussed above, it is likely to detectprimary systems with weaker signal strength than the local noise of theHE.

In some embodiments, the configuration message includes informationregarding the respective predetermined threshold of theprimary-system-feature detection and the method receives the measurementreport sent when the primary-system-feature detection value is less thanthe respective predetermined threshold (i.e., on a C2 event basis) andthen determines, based upon the measurement report, that the at leastone channel has a likelihood of being used by a potential secondarysystem. After that, the method 100 sends a further configuration messagefor periodical reception of a measurement report regarding a measuredsecondary-system-feature detection value. Upon periodical receipt of themeasurement report regarding the measured secondary-system-featuredetection value, the method 100 determines whether to share the at leastone channel with the potential secondary system based upon theperiodically received measurement report. For example, the method 100may determine whether the LTE system can be co-coexisted with thesecondary system by interference coordination. For instance, if thesecondary system is a WiFi system, then it can be determined that boththe LET system and the WiFi system may share this sensed channel. If thesecondary system, however, is a wireless microphone system, then it canbe determined that the LTE system stands no chance of sharing thechannel with the microphone system.

In some embodiments, the configuration message includes informationregarding the respective predetermined threshold of the energy detectionand the method 100 sends, if no reception of a measurement report sentwhen the energy detection value is less than the respectivepredetermined threshold (e.g., due to a large measurement value ormeasurement reporting failure), a further configuration messageincluding information regarding the respective predetermined thresholdof the primary-system-feature detection. Upon receipt of a measurementreport sent when the primary-system-feature detection value is less thanthe respective predetermined threshold (i.e., triggered by a C2 event),the method 100 determines the primary system is absent based upon thereceived measurement report.

It would be understood that no reception of the measurement reporttriggered by a C1 event implies a possibility of a primary system beingpresent and that applying feature detection to the primary system wouldbe a straightforward way to ascertain the existence of the primarysystem.

In some embodiments, the configuration message includes informationregarding the respective predetermined threshold of the energy detectionand the method 100 sends, if no reception of a measurement report sentwhen the energy detection value is less than the respectivepredetermined threshold, a further configuration message for periodicalreception of a measurement report regarding a measuredprimary-system-feature detection value. Upon periodical receipt of themeasurement report regarding the measured primary-system-featuredetection value, the method 100 determines whether the primary system ispresent based upon the periodically received measurement report.

In some embodiments, no measurement report is for reception and themethod 100 sends a further configuration message for periodicalreception of a measurement report regarding a measuredprimary-system-feature detection value or a measuredsecondary-system-feature detection value. Upon receipt of themeasurement report regarding the measured primary-system-featuredetection value or the measured secondary-system-feature detectionvalue, the method 100 determines whether the primary system or thesecondary system is present based upon the periodically receivedmeasurement report. After that, the method 100 determines, if theprimary system is absent and the secondary system is present, whether toshare the at least one channel with the secondary system.

In some embodiments, the measurement report includes informationindicative of the at least one channel.

As will be clear from the above discussion, unlike a prior artmeasurement report, which generally reports the information regardingthe neighboring cell, the measurement report of the present inventionincludes information indicative of the at least one sensed or measuredchannel. In other words, a specific frequency point is reported to theBS in a straightforward way.

From the above discussion with respect to various embodiments of thepresent invention, it would be understood that (coarse) energy or (fine)feature detection may be applied in combination with the reportingtrigger of C1 or C2 event and in some instances, the resultingmeasurement report may also be sent periodically. In this way, a primarysystem can be accurately identified and potential interference betweenthe primary system and the LTE system may be minimized. Meanwhile,valuable spectrum resources would be utilized in a highly-efficientmanner.

FIG. 2 is a flow chart schematically illustrating a method 200 forperforming out-of-band sensing on an unlicensed frequency band from a UEperspective according to another embodiment of the present invention. Asillustrated in FIG. 2, the method 200 begins at step S201, and advancesto step S202, at which the method 200 measures an energy detection valueor a primary-system-feature detection value of a received signal on atleast one channel in a frequency band of a primary system. Followingmeasurements of the energy detection value or the primary-system-featuredetection value of the received signal, the method 200 proceeds to stepS203, at which the method 200 sends a measurement report when themeasured energy detection value or primary-system-feature detectionvalue of the received signal on the at least one channel is less than arespective predetermined threshold of energy detection orprimary-system-feature detection (i.e., on a C1 or C2 event basis).Finally, the method 200 ends at step S204.

In some embodiment, the measuring is based upon a configuration messagereceived from a BS and the configuration message includes the respectivepredetermined threshold of the energy detection orprimary-system-feature detection.

In some embodiments, for a primary system whose signal strength is lowerthan noise strength of a UE, the sending the measurement report to theBS as illustrated in step S203 comprises sending the measurement reportwhen the measured energy detection value is less than the respectivepredetermined threshold and the method 200 further measures theprimary-system-feature detection value of the received signal on the atleast one channel. After the measurement, the method 200 sends ameasurement report when the primary-system-feature detection value isless than the respective predetermined threshold. Alternatively, afterthe measurement, the method 200 periodically sends a measurement reportregarding the primary-system-feature detection value.

In some embodiments, the measured energy detection value andprimary-system-feature detection value are not less than the respectivepredetermined thresholds (i.e., C1 and C2 events are not met) and themethod 200 further measures the primary-system-feature detection valueof the received signal on the at least one channel and periodicallysends a measurement report regarding the primary-system-featuredetection value.

In some embodiments, the primary-system-feature detection value is lessthan the respective predetermined threshold and the method 200 furthermeasures a secondary-system-feature detection value of the receivedsignal on the at least one channel and periodically sends a measurementreport regarding the secondary-system-feature detection value.

In the above some embodiments, the periodically sending the measurementreport is based upon a further configuration message received from a BSand the further configuration message is for configuring periodicalsending of a measurement report. In addition, the measurement report assent by the UE to the BS may include information indicative of the atleast one channel.

The foregoing has discussed some exemplary embodiments of the presentinvention from a UE point of view and the contents (such as details ofC1 or C2 event) identical to those previously discussed in connectionwith FIG. 1 are omitted herein for simplicity. For a betterunderstanding of the present invention, below are examples of signalfeature detection or measurement of the primary and secondary systems.

Example 1 Signal Feature Detection of a Primary System

If the sensed unlicensed band is a TV band, the primary signals could beATSC (North America), DTV-B (Europe), or ISDB (Japan) signals. Here howthe UE performs the feature detection for an ATSC signal will beexemplarily discussed as below.

The ATSC signal has a number of features, such as PN sequence, pilot,segment-synch characteristic, and cyclostationarity property and so on.As specified in 802.22 standards, a pilot detection method is suggestedfor TV signals detection.

The ATSC signal uses a 8-VSB modulation with signal levels (−7, −5, −3,−1, 1, 3, 5, 7). A DC offset of 1.25 is added to this at baseband toeffectively create a small pilot signal to enable carrier recovery atthe receiver. Upon completion of the digital transition, there will beonly two possible pilot frequencies: 309440.6 Hz and 328843.6 Hz. Thedifference between these two pilot frequencies is approximately 19.4kHz.

For UE end that performs the feature detection to check whether thepilot signal exists or not, it should: 1) estimate the PSD of the pilotfrequency on unlicensed band. The midpoint between the two pilotfrequencies is down converted to DC and the signal is filtered with anarrow-band low-pass filter. The filter double-sided bandwidth needs tobe more that 19.4 kHz to ensure that the pilot signal is within thebandwidth of the filter. For instance, the PSD can be estimated using aperiodogram which is based upon the DFT and can be implementedefficiently using the FFT; 2) find the frequency of the maximum of thePSD estimate which should be the ATSC pilot. Then compare this estimatedpilot frequency with the real pilot frequencies, and calculate thesimilarity between them.

In this case, the feature detection value of the primary signal is thesimilarity between the estimated ATSC pilot frequency and real one, andif this feature detection value is smaller than a predeterminedthreshold, then UE reports the result by the event C2, meaning that theprimary signal or system is not present.

Example 2 Signal Feature Detection of a Secondary System

In secondary system coexistence scenario on an unlicensed band, theremay be multiple potential secondary systems, such as WLAN, Bluetooth orother cellular systems. The set of possible systems and theirtransmission parameters might be obtained as prior knowledge to assistcognitive devices in performing feature detection. These parametersinclude bandwidths, modulation types, duplexing, and multiple accessingmethods and so on. For examples, CDMA systems have dedicated spreadingcodes for pilot and synchronization channels and OFDM packets havepreambles for packet acquisition. Different types of modulated signals(such as BPSK, QPSK, and SQPSK) that have identical PSD functions mayhave highly distinct spectral correlation functions. Furthermore,stationary noise and interference exhibit no spectral correlation. Thesesignatures can be used to detect secondary systems on the sensedunlicensed band.

If the possible secondary system is WiFi or WiMax. They are both OFDMsystems, but the frame structure and the length of the CP are different.Therefore, CP-based autocorrelation detection can identify them.

For UE end, it should perform autocorrelation processing for thereceived signal on the sensed band, then obtain the interval andamplitude value of correlation peak. Take the correlation peak intervalas a secondary signal feature, and then the similarity value between itand prior knowledge is calculated. If this feature detection value isless than a predetermined threshold, then UE reports the result by e.g.,the event C2, meaning that the secondary signal does not exist.

Although examples regarding how to measure feature detection values arediscussed herein, a person skilled in the art can understand from theteaching and disclosure of the embodiments of the present invention thatexisting energy detection, spectrum sensing and decision-makingalgorithms may be applied, mutatis mutandis, to the present invention.For example, for the energy detection, a person skilled in the art canapply any suitable approaches to directly measure the energy of thereceived signal on the channel to be sensed and then compare themeasured energy value to the predetermined threshold.

FIG. 3 schematically illustrates signaling process 300 of out-of-bandsensing in a cognitive LET system according to an embodiment of thepresent invention. As illustrated in FIG. 3, the process 300 begins atstep S304 wherein an eNB 302 sends or initiates an admission request toa database 301 such as one used in the TVWS. Then, the process 300proceeds to step S305 at which the database 301 sends an admissionresponse to the eNB 302, wherein the admission response may include butnot be limited to a possible available or target channel list andinformation about a target primary system and other secondary systems.Upon receipt of the admission response, the process 300 proceeds to stepS306, at which the eNB 302, based upon the admission response, configurea periodical or event triggered measurement procedure for a UE 303 via aconfiguration message.

Upon receipt of the configuration information, the UE 303 may, at stepS307 measure energy, primary-system-feature, or secondary-system-featuredetection values of a received signal on the channel to be sensed.Subsequent to the measurement of the values, the process 300 advances tostep S308, at which the UE 303 sends the respective measurement reportevent-triggered or periodically to the eNB 302. At step S309, the eNB302 collects measurement reports from a plurality of UEs including theUE 303 and makes a final decision on a current status of the sensedchannel, i.e., whether the sensed channel is idle or not or whether ithas been occupied by other secondary systems, in which case the eNB 302may further configure a periodical feature detections aimed atdistinguishing or identifying the secondary systems and then schedulethe coexistence strategy between the secondary systems, such as retreat,negotiation or competition. The process 300 then advances to step S310,at which the eNB 302 reports the sensing results to the database 301,which, in turn, at step S311, refreshes or updates the records.

The foregoing briefly discusses the signaling flow of the out-of-bandsensing of some embodiments of the present invention. However, it isonly for illustrative purposes and some steps could be omitted. Forexample, when the database is not available or even does not exist, thensteps S304, S305, S310, and S311 should be omitted. In this case, thefeature-related information may be obtained by the eNB's historicalinformation or empirical values. Additionally, although not discussedabove, it should be noted that multiple measurement instances may, asappropriate, arise among steps S306-S309, as detailed in embodiments inrelation to FIGS. 1 and 2.

FIG. 4 is a schematic diagram illustrating some events that arise in acognitive LTE system. As illustrated in a time-frequency coordinate inFIG. 4, in the frequency band of the LTE system, the existing A4 eventtriggers measurement reports to be sent from the neighbor cells to themiddle serving cell. The existing A2 event triggers measurements withinthe serving cell. For spectrum holes, a measurement report triggered bya C1 event as proposed by the present invention regarding the unlicensedspectrum bands may be sent to the serving cell working under thefrequency band of the LTE system, as shown by an arrow. For spectrumbands occupied by incumbents or secondary systems, measurement reportstriggered by C2 events as proposed by the present invention may be sentto the serving cell under the frequency band of the LTE system, as shownby two arrows.

FIG. 5 is a flow chart schematically illustrating in detail a method 500for performing out-of-band sensing on an unlicensed frequency bandaccording to another embodiment of the present invention. As illustratedin FIG. 5, the method 500 begins at step S501 and proceeds to step S502,at which the method 500 configures, via a configuration message, a UE toperform energy detection and to send to a BS a measurement reporttriggered by a C1 event if the measured energy detection value is lessthan a predetermined threshold. At step S503, the method 500 determineswhether a C1 event triggered report is received or not. If themeasurement report at issue is received by the BS, then at step S504,the method 500 determines the sensed channel is idle and at step S505,the method 500 directs the BS to use this sensed channel by CA oropportunistic secondary access. In this case, the method 500 ends atstep S512.

If the measurement triggered by the C1 event is not received by the BSdue to a large energy measurement value or measurement reportingfailure, the method 500 advances to step S506, at which the method 500configures, via a configuration message, the UE to perform sensing ormeasurement on a C2 event basis, i.e., measurement of aprimary-system-feature detection value. As discussed before, if themeasured detection value is less than a predetermined threshold (“Yes”at step S507), the method 500 then sends a measurement report to the BS.Otherwise, the method 500 advances to step S508, at which the method 500determines that the primary system is present and thus the sensedchannel is unsuitable for the LTE operations. In this case, the method500 ends at step S512.

All things being equal, upon receipt of the measurement report triggeredby the C2 event, the method 500 proceeds to step S509, at which the BSconfigures the UE to perform sensing (i.e., secondary system featuredetection). As discussed previously, to distinguish the secondarysystems, the UE may measure the secondary-system-feature detection valueof the received signal on the channel to be sensed and periodically sendthe measure report to the BS upon determination at step S510. Then, atstep S511, the method 500 judges or determines, by the BS, coexistenceissues with other secondary systems through e.g., interferencecoordination.

It can be noted from the above discussion in connection with the method500 that a number of approaches could be flexibly taken to ascertain theexistence of the primary system and usability of the sensed channel. Inother words, according to embodiments of the present invention,periodical reporting and C1 and C2 event triggered reporting mechanismscan be used separately or in any suitable combination manners so as toferret out usable channels in the unlicensed frequency band.

In addition, the method 500 may involve further implemental details;however, the present invention is not limited thereto. Further, itshould be noted herein that the steps and execution order as illustratedFIG. 5 are only examples and are not restrictive to the presentinvention. Those skilled in the art, after reading the presentspecification, can change these steps, for example, by omitting,combining, or adding certain steps, changing the execution order ofcertain steps so as to adapt to different application demands. Forexample, if the BS determines it may be better to perform primaryfeature detection first, then steps S502-S505 in the method 500 may beomitted. Additionally, according to different measurementconfigurations, the embodiments of the present invention can beadvantageously applied to sense any suitable spectrum.

FIG. 6 illustrates a simplified block diagram of a BS 601 and a UE 602that are suitable for use in practicing the exemplary embodiments of thepresent invention. In FIG. 6, a wireless network is adapted forcommunication with the UE 602, which may be configured with capabilitiesof out-of-band sensing (e.g., by coarse and fine sensing, and reportingby a respective C1 or C2 event), via the BS (or eNB) 601. The UE 602includes a data processor (DP) 603, a memory (MEM) 604 coupled to the DP603, and a suitable RF transmitter TX and receiver RX 605 (which neednot be implemented in a same component) coupled to the DP 603. The MEM604 stores a program (PROG) 606. The TX/RX 605 is for bidirectionalwireless communications with the BS 601. Note that the TX/RX 605 has atleast one antenna to facilitate communication; multiple antennas may beemployed for multiple-input multiple-output MIMO communications in whichcase the UE 602 may have multiple TXs and/or RXs.

The BS 601 includes a data processor (DP) 607, a memory (MEM) 608coupled to the DP 607, and a suitable RF transmitter TX and receiver RX609 coupled to the DP 607. The MEM 608 stores a program (PROG) 610. TheTX/RX 609 is for bidirectional wireless communications with the UE 602.Note that the TX/RX 609 has at least one antenna to facilitatecommunication, though in practice a BS will typically have several. TheBS 601 may be coupled via a data path to one or more external networksor systems, such as the internet, for example.

At least one of the PROGs 606 and 610 is assumed to include programinstructions that, when executed by the associated DPs 603 and 607,enable the UE 602 and BS 601 to operate in accordance with the exemplaryembodiments of this invention, as discussed herein with the methods 100,200, 300, and 500.

In general, the various embodiments of the UE 602 can include, but arenot limited to, cellular phones, personal digital assistants (PDAs)having wireless communication capabilities, portable computers havingwireless communication capabilities, image capture devices such asdigital cameras having wireless communication capabilities, gamingdevices having wireless communication capabilities, music storage andplayback appliances having wireless communication capabilities, Internetappliances permitting wireless Internet access and browsing, as well asportable units or terminals that incorporate combinations of suchfunctions.

The embodiments of the present invention may be implemented by computersoftware executable by one or more of the DPs 603, 607 of the UE 602 andthe BS 601, or by hardware, or by a combination of software andhardware.

The MEMs 604 and 608 may be of any type suitable to the local technicalenvironment and may be implemented using any suitable data storagetechnology, such as semiconductor based memory devices, magnetic memorydevices and systems, optical memory devices and systems, fixed memoryand removable memory, as non-limiting examples. While only one MEM isshown in the BS 601 or UE 602, there may be several physically distinctmemory units in the BS 601 or UE 602. The DPs 603 and 607 may be of anytype suitable to the local technical environment, and may include one ormore of general purpose computers, special purpose computers,microprocessors, digital signal processors (DSPs) and processors basedon multicore processor architecture, as non limiting examples. Either orboth of the UE 602 and the BS 601 may have multiple processors, such asfor example an application specific integrated circuit chip that isslaved in time to a clock which synchronizes the main processor.

Exemplary embodiments of the present invention have been described abovewith reference to block diagrams and flowchart illustrations of methods,apparatuses (i.e., systems). It will be understood that each block ofthe block diagrams and flowchart illustrations, and combinations ofblocks in the block diagrams and flowchart illustrations, respectively,can be implemented by various means including computer programinstructions. These computer program instructions may be loaded onto ageneral purpose computer, special purpose computer, or otherprogrammable data processing apparatus to produce a machine, such thatthe instructions which execute on the computer or other programmabledata processing apparatus create means for implementing the functionsspecified in the flowchart block or blocks.

The foregoing computer program instructions can be, for example,sub-routines and/or functions. A computer program product in oneembodiment of the invention comprises at least one computer readablestorage medium, on which the foregoing computer program instructions arestored. The computer readable storage medium can be, for example, anoptical compact disk or an electronic memory device like a RAM (randomaccess memory) or a ROM (read only memory).

Many modifications and other embodiments of the inventions set forthherein will come to mind to one skilled in the art to which theseembodiments of the invention pertain having the benefit of the teachingspresented in the foregoing descriptions and the associated drawings.Therefore, it is to be understood that the embodiments of the inventionare not to be limited to the specific embodiments disclosed and thatmodifications and other embodiments are intended to be included withinthe scope of the appended claims. Although specific terms are employedherein, they are used in a generic and descriptive sense only and notfor purposes of limitation.

1. A method, comprising: sending a configuration message for configuringmeasurement on at least one channel in a frequency band of a primarysystem; receiving a measurement report made based upon the configurationmessage; and determining the usability of the at least one channel basedupon the measurement report, wherein the configuration message includesinformation regarding a respective predetermined threshold of energydetection or primary-system-feature detection, and the measurementreport is for reception when a measured energy detection value or ameasured primary-system-feature detection value of a received signal onthe at least one channel is less than the respective predeterminedthreshold.
 2. The method as recited in claim 1, wherein theconfiguration message includes the information regarding the respectivepredetermined threshold of the energy detection, and wherein the methodcomprises: receiving the measurement report sent when the measuredenergy detection value is less than the respective predeterminedthreshold; and determining that the at least one channel is usable forcellular communication based upon the measurement report.
 3. The methodas recited in claim 1, wherein the configuration message includesinformation regarding the respective predetermined threshold of theenergy detection, and wherein the method comprises: receiving themeasurement report sent when the measured energy detection value is lessthan the respective predetermined threshold; sending a furtherconfiguration message including information regarding the respectivepredetermined threshold of the primary-system-feature detection;receiving a further measurement report sent when a measuredprimary-system-feature detection value is less than the respectivepredetermined threshold; and determining the primary system is absentbased upon the further measurement report.
 4. The method as recited inclaim 1, wherein the configuration message includes informationregarding the respective predetermined threshold of the energydetection, and wherein the method comprises: receiving the measurementreport sent when a measured energy detection value is less than therespective predetermined threshold; sending a further configurationmessage for periodical reception of a measurement report regarding ameasured primary-system-feature detection value; periodically receivingthe measurement report regarding the measured primary-system-featuredetection value; and determining whether the primary system is presentbased upon the periodically received measurement report.
 5. The methodas recited in claim 4, wherein signal strength of the primary system islower than noise strength of a user equipment.
 6. The method as recitedin claim 1, wherein the configuration message includes informationregarding the respective predetermined threshold of theprimary-system-feature detection, and wherein the method comprises:receiving the measurement report sent when the primary-system-featuredetection value is less than the respective predetermined threshold;determining, based upon the measurement report, that the at least onechannel has a likelihood of being used by a potential secondary system;sending a further configuration message for periodical reception of ameasurement report regarding a measured secondary-system-featuredetection value; periodically receiving the measurement report regardingthe measured secondary-system-feature detection value; and determiningwhether to share the at least one channel with the potential secondarysystem based upon the periodically received measurement report.
 7. Themethod as recited in claim 1, wherein the configuration message includesinformation regarding the respective predetermined threshold of theenergy detection, and wherein the method comprises: sending, if noreception of a measurement report sent when the energy detection valueis less than the respective predetermined threshold, a furtherconfiguration message including information regarding the respectivepredetermined threshold of the primary-system-feature detection;receiving a measurement report sent when the primary-system-featuredetection value is less than the respective predetermined threshold; anddetermining the primary system is absent based upon the receivedmeasurement report.
 8. The method as recited in claim 1, wherein theconfiguration message includes information regarding the respectivepredetermined threshold of the energy detection, and wherein the methodcomprises: sending, if no reception of a measurement report sent whenthe energy detection value is less than the respective predeterminedthreshold, a further configuration message for periodical reception of ameasurement report regarding a measured primary-system-feature detectionvalue; periodically receiving the measurement report regarding themeasured primary-system-feature detection value; and determining whetherthe primary system is present based upon the periodically receivedmeasurement report.
 9. The method as recited in claim 1, wherein nomeasurement report is for reception, and wherein the method furthercomprises: sending a further configuration message for periodicalreception of a measurement report regarding a measuredprimary-system-feature detection value or a measuredsecondary-system-feature detection value; periodically receiving themeasurement report regarding the measured primary-system-featuredetection value or the measured secondary-system-feature detectionvalue; determining whether the primary system or the secondary system ispresent based upon the periodically received measurement report; anddetermining, if the primary system is absent and the secondary system ispresent, whether to share the at least one channel with the secondarysystem.
 10. The method as recited claim 1, wherein the measurementreport includes information indicative of the at least one channel. 11.A method, comprising: measuring an energy detection value or aprimary-system-feature detection value of a received signal on at leastone channel in a frequency band of a primary system; and sending ameasurement report when the measured energy detection value orprimary-system-feature detection value of the received signal on the atleast one channel is less than a respective predetermined threshold ofenergy detection or primary-system-feature detection.
 12. The method asrecited in claim 11, wherein the measuring is based upon a configurationmessage received from a base station and the configuration messageincludes the respective predetermined threshold of the energy detectionor primary-system-feature detection.
 13. The method as recited in claim11, wherein the sending the measurement report comprises sending themeasurement report when the measured energy detection value is less thanthe respective predetermined threshold, and wherein the method furthercomprises: measuring the primary-system-feature detection value of thereceived signal on the at least one channel; and sending a measurementreport when the primary-system-feature detection value is less than therespective predetermined threshold.
 14. The method as recited in claim11, wherein the sending the measurement report comprises sending themeasurement report when the measured energy detection value is less thanthe respective predetermined threshold, and wherein the method furthercomprises: measuring the primary-system-feature detection value of thereceived signal on the at least one channel; and periodically sending ameasurement report regarding the primary-system-feature detection value.15. The method as recited in claim 13, wherein signal strength of theprimary system is lower than noise strength of a user equipment.
 16. Themethod as recited in claim 11, wherein the measured energy detectionvalue and primary-system-feature detection value are not less than therespective predetermined thresholds, and wherein the method furthercomprises: measuring the primary-system-feature detection value of thereceived signal on the at least one channel; and periodically sending ameasurement report regarding the primary-system-feature detection value.17. The method as recited in claim 11, wherein theprimary-system-feature detection value is less than the respectivepredetermined threshold, and wherein the method further comprises:measuring a secondary-system-feature detection value of the receivedsignal on the at least one channel; and periodically sending ameasurement report regarding the secondary-system-feature detectionvalue.
 18. The method as recited in claim 14, wherein the periodicallysending is based upon a further configuration message received from abase station and the further configuration message is for configuringperiodical sending of a measurement report.
 19. The method as recited inclaim 11, wherein the measurement report includes information indicativeof the at least one channel.
 20. (canceled)
 21. (canceled)
 22. Anapparatus, comprising: at least one processor and at least one memoryincluding compute program code, the memory and the computer program codeconfigured to cause the apparatus to at least: send a configurationmessage for configuring measurement on at least one channel in afrequency band of a primary system; receive a measurement report madebased upon the configuration message; and determine the usability of theat least one channel based upon the measurement report, wherein theconfiguration message includes information regarding a respectivepredetermined threshold of energy detection or primary-system-featuredetection, and the measurement report is for reception when a measuredenergy detection value or a measured primary-system-feature detectionvalue of a received signal on the at least one channel is less than therespective predetermined threshold.
 23. An apparatus, comprising: atleast one processor and at least one memory including compute programcode, the memory and the computer program code configured to cause theapparatus to at least: measure an energy detection value or aprimary-system-feature detection value of a received signal on at leastone channel in a frequency band of a primary system; and send ameasurement report when the measured energy detection value orprimary-system-feature detection value of the received signal on the atleast one channel is less than a respective predetermined threshold ofenergy detection or primary-system-feature detection.
 24. Anon-transitory computer-readable storage medium including program codewhich when executed by at least one processor causes operationscomprising: sending a configuration message for configuring measurementon at least one channel in a frequency band of a primary system;receiving a measurement report made based upon the configurationmessage; and determining the usability of the at least one channel basedupon the measurement report, wherein the configuration message includesinformation regarding a respective predetermined threshold of energydetection or primary-system-feature detection, and the measurementreport is for reception when a measured energy detection value or ameasured primary-system-feature detection value of a received signal onthe at least one channel is less than the respective predeterminedthreshold.
 25. A non-transitory computer-readable storage mediumincluding program code which when executed by at least one processorcauses operations comprising: measuring an energy detection value or aprimary-system-feature detection value of a received signal on at leastone channel in a frequency band of a primary system; and sending ameasurement report when the measured energy detection value orprimary-system-feature detection value of the received signal on the atleast one channel is less than a respective predetermined threshold ofenergy detection or primary-system-feature detection.